The invention relates to an optical storage apparatus using a removable medium such as an MO cartridge or the like and, more particularly, to an optical storage apparatus for efficiently adjusting a light emitting power of a laser diode to an optimum power when a medium is loaded.
Attention is paid to an optical disk as a storage medium serving as a core of multimedia which is rapidly developing in recent years. When considering an MO cartridge of 3.5 inches as an example, media of a high density recording of 540 MB and 640 MB have been provided in recent years in addition to the conventional media of 128 MB and 230 MB. Therefore, it is desirable in an optical disk drive that all of the media of 180 MB, 230 MB, 540 MB, and 640 MB which are available at present can be used. In the MO cartridge which is used in the optical disk drive, a ZCAV recording (zone constant angular velocity recording) in which a medium track is divided into zones and the number of sectors in each zone is set to be equal is used. The number of zones of the MO medium is equal to 1 zone in case of the conventional medium of 128 MB and 10 zones in case of the medium of 230 MB. In case of the media of 640 MB and 540 MB which have been put into practical use in recent years, the numbers of zones are equal to 11 zones and 18 zones, respectively.
A recording method of the conventional media of 128 MB and 230 MB is a pit position modulation (PPM). In the PPM recording, a light emitting power is changed at three stages of a reading power, an erasing power, and a recording power. As compared with those media, a recording method of the media of 540 MB and 640 MB is a pulse width modulation (PWM). The PWM recording is also called a pulse train recording. In the PWM recording, the light emitting power is changed at four stages of the reading power, erasing power, and first and second writing powers. In case of the PWM recording for a medium of a direct overwrite correspondence type, since it is unnecessary to erase, the light emitting power is changed at four stages of the reading power, assisting power, first writing power, and second writing power. The assisting power gives a specified power for raising a response speed of a medium heating to write by the first or second writing power.
Ordinarily, in case of a removable optical disk medium enclosed in the cartridge, since an optimum recording power differs every medium, a light emitting adjustment such that when the medium is loaded, a test writing is performed every zone and the power is adjusted to the optimum recording power is executed. However, when a pitch between tracks is narrowed in order to realize a high density of the optical disk medium, a heat conduction easily occurs in an adjacent track. Consequently, even if the optimum recording power is determined by performing the test writing by a laser diode, although the recording can be properly executed to a target track, there is considered a possibility of occurrence of problems such that data on the adjacent track is erased, data of the adjacent track leaks, and the like.